Example of adding an icon to the Control Strip region of the Mac Touch Bar using a headless/UI-less background app. Icon is always displayed, regardless of which app is in the foreground.
Uses a private API, not suitable for the App Store.
No XCode project, no Nib/Xib, builds from command-line. Just the minimum necessary to add an always-available button to the Control Strip.
Inspired by: https://github.com/a2/touch-baer
$ make
$ make run
$ make kill
$ make clean
Links against private framework DFRFoundation.
Uses two DFRFoundation functions: DFRElementSetControlStripPresenceForIdentifier and DFRSystemModalShowsCloseBoxWhenFrontMost
Uses private NSTouchBarItem method: +(void)addSystemTrayItem:(NSTouchBarItem *)item;
Uses private NSTouchBar method: +(void)presentSystemModalFunctionBar:(NSTouchBar *)touchBar systemTrayItemIdentifier:(NSString *)identifier;
Simply creates a windowless NSApplication and an NSApplicationDelegate implementing the private functions.
MUST execute from a mac .app bundle. The TouchBar service doesn't seem to communicate with a binary when launched outside of a bundle. I did not investigate why.